Exterior aerodynamic fairings mounted across hinged surfaces can have unacceptable gaps between the fairing attached to the rudder and the mating fairing attached to the rudder tab. Ideally, these two mating fairings should match to the extent that they overlap to provide a continuous contour, and they do not interfere with each other during their full range of required relative motion about the hinge line. This problem is especially pronounced when the hinge line is not perpendicular to the longitudal axis of the fairing parts, which must be aligned with the air flow to keep aerodynamic drag to an acceptable level. In a recent aircraft design effort, the push rod fairings on the rudder and tab were originally designed with a contour that minimized the frontal area for drag purposes. These two-piece fairings required redesigned edge shapes to eliminate physical interferences during movement about the hinge line. This resulted in gaps which can cause undue air leakage and drag, and also darkened gap areas that create an unfavorable aesthetic impression for airline customers.
U.K. Patent Application GB 2238991A to Williams et al. describes fairings designed to cover a wing control surface actuating mechanism that has one segment attached to the wing, and one segment to a control surface and a center section made out of a flexible material that slides inside the other sections and deforms as needed to match their shapes.
U.S. Pat. No. 5,071,092 to Williams et al. (two common co-inventors with U.K. patent discussed above) also related to the wing to control surface actuator fairing. Multiple, overlapping layers of thin strips attached to the wing side of the fairing and projecting back over the surface of the control surface side. They are pushed aside by the rear fairing section when the control surface moves, but their spring force keeps them pressed against it.
U.S. Pat. No. 4,854,528 to Hofrichter discusses a fairing for a flap control system that is divided into three segments, the motions of which are controlled by the flap mechanism so that they move with it and slide within one another to maintain a continuous fairing.
U.S. Pat. No. 5,388,788 to Rudolph, assigned to the asignee of this invention, discloses a fairing for a hinged control surface in which the lower surface of the movable surface is also cylindrically curved. Thus, a flush surface is presented at all angles of the control surface, and there is, available between the two curved fairing surfaces, a curved load path for the actuating mechanism so that it does not need to penetrate the outer envelope of the normal aerodynamic surface.
The problems discussed above are illustrated and described in terms of a rudder and rudder tab assembly. Similar problems may also apply to other types of control surfaces such as ailerons, leading and trailing edge flaps, elevators and the like.